var h3s = document.getElementsByTagName('h3');
for (var i = 0; i < h3s.length; i++) {
    h3s[i].onclick = function() {
        //先隐藏ilist
        for (var j = 0; j < h3s.length; j++) {
            h3s[j].nextElementSibling.style.display = 'none';
        }
        var nextSibling = this.nextElementSibling; //h3获取下一个兄弟元素就是三个li
        nextSibling.style.display = 'block';
    }
}